Production of polyamino acid solution in alcoholic solvents

ABSTRACT

A UNIQUE POLYAMINO ACID SOLUTION IS OBTAINED BY DISSOLVING A POLYAMINO ACID IN A SOLVENT SYSTEM CONTAINING AT LEAST ONE SOLVENT SELECTED FROM THE GROUP CONSISTING OF FURFURYL ALCOHOL, 1,3-DICHLORO-2-PROPANOL, AND 2,3-DICHLORO-1-PROPANOL.

United States Patent Olfice US. Cl. 260-304 N 28 Claims ABSTRACT OF THE DISCLOSURE A unique polyamino acid solution is obtained by dissolving a polyamino acid in a solvent system containing at least one solvent selected from the group consisting of furfuryl alcohol, 1,3-dichloro-2-propanol, and 2,3-dichloro-l-propanol The present invention relates to a polyamino acid solution. More particularly, it relates to a polyamino acid solution having a solvent system containing furfuryl alcohol (hereinafter referred to as FA), 1,3-dichloro-2-porpanol (hereinafter referred to as 1,3-DCP) or 2,3-dichloro-l-propanol (hereinafter referred to as 2,3-DCP).

In this specification, the term polyamino acids includes homopolymers and copolymers of amino acids and/ or derivatives thereof having a degree of polymerization of 50 to 5,000 and containing a repeating unit in the polymer molecule obtaining from the following monomers:

(1) w-esters of acidic amino acids such as B-alkyl aspartate, 'y-alkyl glutamate, etc. (wherein the alkyl group has 1 to 18 carbon atoms, preferably 1 to 8 carbon atoms and includes methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl and octyl).

(2) N'-substituted basic amino acids such as N-substituted ornithine, N -substituted lysine (wherein the substituents include aromatic acyl groups having 7 to 8 carbon atoms, alicyclic acyl groups having 4 to 8 carbon atoms, aliphatic acyl groups having 2 to 8 carbon atoms, these acyl groups being exemplified by benzoyl, cyclohexylcarbonyl, acetyl, propionyl, butyryl, pentanoyl, hexanoyl, heptanoyl, octanoyl, etc., and also include aromatic oxycarbonyl groups having 7 to 8 carbon atoms, alicyclic oxycarbonyl groups having 4 to 8 carbon atoms, aliphatic oxycarbonyl groups having 2 to 8 carbon atoms, these oxycarbonyl groups being exemplified by carbobenzoxy, cyclohexyloxycarbonyl, methoxycarbonyl, ethyloxycarbonyl, propyloxycarbonyl, butyloxycarbonyl, pentyloxycarbonyl, hexyloxycarbonyl, heptyloxycarbonyl, etc.), etc.

(3) neutral amino acids free of hydroxyl groups having 2 to 9 carbon atoms, such as glycine, valine, leucine, isoleucine, phenylalanine, methionine, etc. (the amino acids forming monomers (1) to (3) may be optically active or inactive) or (4) D-alanine or L-alanine.

Polyamino acids are used as a material for producing synthetic leathers in the form of a film or the like and synthetic fibers. They are also useful as a top-coating agent of natural and synthetic leathers.

These polyamino acids decompose upon heating and cannot exist in a melted state. Therefore, to produce shaped articles, a melt-shaping process cannot be employed and the shaping is inevitable effected by either a wet process or a dry process. Accordingly, in order to obtain shaped articles of polyamino acids, it is usually necessary to prepare a polyamino acid solution.

Polyamino acids which may be exemplified by poly- 7-methylglutamate are prepared by polymerizing amino acid N-carboxy anhydrides which are monomers in a suitable solvent such as, for example, ethylene dichloride.

3,822,231 Patented July 2, 1974 However, the polyamino acid solution after polymerization contains polymers having various degrees of polymerization and also unreacted monomers. Accordingly, it is often disadvantageous to use solution directly in the shaping processes.

Ethylene dichloride, ethylene dichloride-trichloroethylene, and ethylene dichloride-tetrachloroethylene are the solvents which are most commonly used for the polymerization reaction. Since these solvents are hydrophobic, when a polymerization solution of polyamino acids in any of these solvents is used for wet shaping, water cannot be used as a coagulating bath; although it is the most inexpensive and easiest bath to handle. Therefore, the use of an organic solvent such as ketones, alcohols, etc. is unavoidable.

Addition of hyrophilic solvents to the polyamino acid solution may be proposed so as to give a hydrophilic nature to the solution. However, since ordinary hydrophilic solvents are usually poor solvents for polyamino acids, the addition thereof often causes the precipitation of the polyamino acids.

When a polyamino acid solution is used as a topcoating agent, usually spray-coating is employed. In this case, in order to control the evaporation speed of the solvent, it is necessary to add, to the polyamino acid solution, other volatile solvents such as dioxane, N,N-dimethylformamide, ethyl acetate, toluene, methyl cellosolve acetate, dimethyl sulfoxide, N-methylpyrrolidone, butanol, methyl isobutyl ketone, etc. These volatile solvents are also poor solvents for polyamino acids and the addition thereof likewise may cause precipitation of polyamino acids.

Further, it is sometimes necessary to precipitate the polyamino acid out of the polymerization solution in order to control the distribution of the molecular weight and to remove impurities. However, once obtained as a precipitate, the polyamino acid is hardly soluble even in ethylene dichloride, ethylene dichloride-trichloroethylene or ethylene dichloride-tetrachloroethylene.

For these reasons, it has been desired to find a hydrophilic solvent for polyamino acids which is capable of highly dissolving polyamino acids and which, when a polyamino acid is dissolved in such a solvent, allows the addition of remarkable amounts of poor solvents for polyamino acids to the resultant polyamino acid solution without causing precipitation of the polyamino acids but at the same time with maintaining the mixed solvent system hydrophilic.

Heretofore, as hydrophilic solvents for polyamino acids, dichloroacetic acid, trifluoroacetic acid, ethylene chlorohydrin, etc. have been known. Dichloroacetic acid and trifiuoroacetic acid readily dissolve solid polyamino acids. However, these solvents are not practical because they are highly corrosive and expensive. Ethylene chlorohydrin (Japanese Patent Publication No. 20,431/ 1964) dissolves polyamino acids at a concentration of only about 10%.

In an attempt to find a solvent which meets the above requirements, the present inventors previously have found that certain kinds of N-substituted heterocyclic compounds such as N-methyl-a-pyrrolidone, morpholine, etc. and certain kinds of aromatic alcohols, such as benzyl alcohols, etc. are useful (respectively US. application Ser. No. 813,308, filed on Apr. 3, 1969 and US. application Ser. No. 834,509, filed on June 18, 1969). However, these solvents are still unsatisfactory in that such solvents are not capable of highly dissolving polyamino acids at room temperature and that when a polyamino acid is dissolved in these solvents, it is not possible to add a large amount of hyrophobic solvents to the resultant polyamino acid solution.

It has now been found that FA, 1,3-DCP and 2,3-DCP can dissolve polyamino acids at a high concentration and a remarkable amount of poor solvents can be added to a polyamino acid solution in at least one of these solvents, without causing precipitation of the polyamino acids but at the same time with keeping the mixed solvent system hydrophilic. Further, similar effects can be expected when FA, 1,3-DCP or 2,3-DCP is added to a polyamino acid solution employing the conventional solvents. Furthermore, a solid polyamino acid once separated out of a polyamino acid solution can be again dissolved by adding FA, 1,3-DCP or 2,3-DCP.

Such a polyamino acid solution is exceedingly useful for shaping processes, for example, a wet-shaping process, dry-shaping process or spray-coating.

Accordingly, one object of the present invention is to provide a new polyamino acid solution.

Another object of the present invention is to provide a polyamino acid solution in a solvent system containing FA, 1,3-DCP, 2,3-DCP, or a mixture thereof.

A further object of the invention is to provide a polyamino acid solution in a mixed solvent system of FA,

1,3-DCP or 2,3-DCP, and poor solvents for polyamino acids.

A still further object of the invention is to provide a new polyamino acid solution in a hydrophilic solvent.

A still further object is to provide a polyamino acid solution suitable for a wet-shaping process, dry-shaping process and spray-coating.

A still further object is to provide a polyamino acid solution in which a solid polyamino acid is dissolved.

Yet another object is to provide a polyamino acid solution with which water may be used as a coagulating bath for the polyamino acid.

Other objects will become apparent from the detailed description given hereinbelow.

The polyamino acid solution according to the present invention may be prepared by adding FA, 1,3-DCP or 2,3-DCP to a solid polyamino acid and stirring at room temperature or with heating. Also the desired polyamino acid solution may be prepared by carrying out a polymerization reaction in one of these solvents. Alternatively the polyamino acid solution may be prepared by carrying out the polymerization reaction in other solvents, for example, ethylene dichloride and adding FA, 1,3-DCP r 2,3-DCP to the solution after the reaction while distilling 01f the solvent to effect substitution of the solvent. If the solvent of the polymerization reaction is allowable to be present in the desired solution, the desired polyamino acid solution can be prepared by simply admixing FA, 1,3-DCP or 2,3-DCP with the solution obtained after the polymerization. It will be recognized that the polyamino acid solution of the present invention is not limited to one that contains only one of FA, 1,3-DCP and 2,3- DCP, but the solution may contain a mixture of any two or all of these solvents.

FA, 1,3-DCP and 2,3-DCP dissolve solid polyamino acids which are rich in the a-helix structures obtained by adding poor solvents to a polymerization solution of a polyamino acid to precipitate the polyamid acid and by isolating the precipitate. FA, 1,3-DCP, and 2,3-DCP dissolve these solid polymers, respectively, at a concentration of 30%, 70% and 70% by weight at room temperature. (Unless otherwise noted, percent shows weight percent throughout the specification.) Further, it is a surprising fact that these three solvents can readily dissolve those solid polyamino acids which are rich in fir-configurations induced by applying mechanical and thermal stresses to said solid polyamino acids, at a high concentration (e.g. FA 15%, 1,3-DCP 50%, and 2,3-DCP 50% at room temperature).

The thus-prepared polyamino acid solution in FA, 1,3- DCP or 2,3-DCP can be directly subjected to a wet or dry-shaping process or spray-coating. However, not only from the economical point of view but also from the reasons already mentioned, consideration must be given to provide improved properties to the polyamino acid solution by adding other solvents thereto without depending only on FA, 1,3-DCP and 2,3-DCP as a solvent. As mentioned above, FA, 1,3-DCP and 2,3-DCP can dissolve polyamino acid at a high concentration. Further, to the resultant solution can be added a large amount of hydrophilic solvents which are poor solvents for polyamino acids, such as methanol, ethanol, propanol, butanol, acetone, methyl ethyl ketone, etc. without causing the precipitation of polyamino acids. This means that when a polyamino acid is subjected to a wet film-forming process, the coagulation time can be controlled, resulting in an advantage in the industrial practice. In adding the above-described hydrophilic, poor solvents for polyamino acids to the polyamino acid solution in FA, 1,3-DCP or 2,3-DCP, the amount of addition may be determined depending upon the purpose of addition. The upper limit of addition varies depending upon the kind of the solvents of the solution, concentration of polyamino acid or kind of the poor solvents. In the case of a 10% FA, 1,3-DCP or 2,3-DCP solution of polyamino acid, usually the upper limit of poor solvent addition is 20 to 30% based on the weight of the solution. Especially, it is allowable to add up to 50% of methyl ethyl ketone, diacetone alcohol or dioxane to the 10% FA solution and up to 50% of ethanol, N,N-dimethylformamide or dimethyl sulfoxide to the 10% 1,3-DCP or 10% 2,3-DCP solution.

Tables 1 and 2 show the coagulation time when solutions of poly-y-methyl-L-glutamate (intrinsic viscosity: 1.8 and molecular weight of 340,000), respectively, in FA and 1,3-DCP are coated on glass plates with a doctor blade having a thickness of 3 mils (V inches) and the coated layers are coagulated in water at 20 C.

TABLE 1 Solution of Coagulation poly-'y-methyl-L-glutamate time (seconds) 30% in FA 20 20% in FA 20 10% in FA 20 10% in FA-+30% of methanol 15 10% in FA+30% of ethanol 1s 10% in FA+30% of isopropanol 15 10% in FA+30% of dioxane 1 20 Added based on the weight of the polyamino acid solution.

TABLE 2 Solution of Coagulation poly-'y-methyl-L-glutamate time (seconds) 60% in 1,3-DCP about 110 30% in 1,3-DCP about 70 20% in 1,3-DCP about 30 10% in 1,3-DCP about 20 10% in 1,3-DCP+30% of ethanol 1 about 20 10% in l,3-DCP,-+20% of dioxane 1 about 20 1 See footnote 1, Table 1.

Tables 3 and 4 show the results when the poly-'y-methyl- L-glutamate (intrinsic viscosity: 1.8) is dissolved in FA and 1,3-DCP, respectively, to prepare solutions having polymer concentrations of 30%, 20%, 15% and 10% and the solutions are diluted with various hydrophilic solvents.

TABLE 3 Concentration of poly--ymethyl-L-glutamate in FA Coagulation time Solvent 10% 15% 20% 30% (seconds) Methanol A X X X 15-20 Ethanol A X X X 10-15 Isopropanol- A X X X 20-25 t-Butanol. A X X X 1520 Diacetone alcoho O A X X 15-20 Meth ethyl ketone- O 8 A X 15-20 Dioxane O A X 20 Tetrahydroluran A X X X 15-20 N ,N-dimethyliormami A X X X 20 Ethylene glycol A X X X 20-25 Acetonitrile A X X X 15-20 Dimethyl sulioxide. O A X X 15-20 Acetone O X X X 10-15 N o'rE.-See footnotes at end of Table TABLE 4 TABLE 6 Concentration of poly-'y- Concentration of polymethyl-L-glutamate in FA Coagu1a 'y-methyl-L-glutation time mate in 1,3-DCP Coagula- Solvent 10% 15% 20% 30% (seconds) 8 1 tion time o vent 10 20 30 Methanol A x x X 15-20 5 (Seconds) O A X 1 -20 Ethyl acetate A X X 20-30 A X X X 20-25 Butyl acetate A X X 20-30 A X X X 15-20 Amy] acetate X X X 20-30 A X X X 15-20 Dichloroethane.. 20-30 A A X X 15-20 Tetrachloroethylene- O A X 20-30 A A X X 1 -20 10 Benzene 30-35 A X X X 15-20 Toluene- 30-35 O O O A 15cm) Xylene 30-35 A X X X 20-25 Ethylene glycol monoethyl ether.-- X X X 20-30 A X X X Ethylene glycol monoethyl ether O A X X 15-20 acetate X X 30-35 Acetone A X X X 1 -1 Ethylene glycol monomethyl ether I acetate X X 30-35 *The coagulation time is measured when the solutlon 0f poly-vn-H xane X X X 30-35 methyl-L-glutamate is diluted to 7 to 8% with the hydrophilic solvent and coated on a glass plate with a doctor blade of 3 mil s to form a coated Th coagulation tim is measured when the 10% solution of poly-yy and the coated layer 15 snbiected to coagulation 111 Water at methyl-L-glutamate is diluted to 7 to 8% with the hydrophobic solvent .O= add the case of the 80100011) or and coated on a glass plate with a doctor blade 013 mils to form a coated (1Y1 1111851050 0511116 1,3-DCP 50111111011) 0f the hydrophlhqsolvent based on layer, and the coated layer is subjected to coagulation in water at 20 C. e w t of t e corresponding FA 0r 3- 2 Solutwn to the FA or =Allowable to add up to 20,000% 200 fold) of the solvent based on 1,3-DCB S ut o t e lndlcatejififllwentfatlonsthe weight of FA or 1,3-DCP solution to the corresponding FA or 1,3-

A=Shght gelation by the addition of 20 to 30% of the solvent. 20 P solution,

e t o or p p ta by the addition of 10 to of the O=Allowable to add 30% (in the case of the FA solution) or 50% (in solvent. the case of the 1,3-DCP solution) of the solvent based on the weight of the corresponding FA or 1,3-DCP solution to the FA or 1,3-DCP solution at the indicated concentrations.

Furthermore, 1t is possible to add a large amount of hy- A=Slight gelation by the addition of 2c t 30% of the solvent. drophobic, poor solvents for polyamino acids to a poly X= Gelation or precipitationbythe additionoi mm 20% of the solvent. p and solutior} Wlthout Similar results are obtained when 2,3-DCP is used in causmg the precipitation of polyamino acids. These hyplace of 1 3 DcPinTab1eS 4 and 6 drqphoblc Poor. solvfmts mclllde ammanc. hydrgqarbons The conventional polyamino acid solution in halogenwhlch l rdauvely mexlfenslve and low In toxmty and .ated hydrocarbons, such as ethylene dichloride, etc. has also vanous other orgamc solvents Exemplary of these far larger specific gravity than water and therefore it has Solvents are benzene toluene i ethyl acetate butyl been difiicult to prepare an emulsion of polyamino acids i i That Such hydr9phoblc poor solYents fol-PO13" in water. In this respect, the polyamino acid solution acamino aclds can.be adfied 1s ildvamageous m that m cording to the present invention overcomes the difi'lculty, plymg a polyammo acld solution to natural a Synthetl; since it allows the addition of various hydrophilic or hyaeathers by Spraycoatmg the evaporatlon speed 9 drophobic solvents having a smaller specific gravity than the solvent can be controlled. Further, the polyamino acid water without causing the precipitation of polyamino l p m F or 1S mamtamed .hydmacids and therefore a polyamino acid solution having a 13.111110 even If such hydrophoblc cuts are added m l specific gravity close to that of water can be prepared. slderable afnwnts and can be S.ub]ected F 3 wet'shapmg The hydrophilic and hydrophobic solvents shown in the process P water or a.solutlon contammg.water as a 40 foregoing tables are used for the preparation of pigment coaglflatmg bath In addmg the .abovefdescnlied p pastes for polymers. The addititon of such a solvent to the Phoblc poor Solvents to polyammo and 9 9 m conventional polyamino acid solution in halogenated hyor 3 the amount of addmon. i deter drocarbons sometimes causes a considerable increase in mmed P upon h purpose of addmon The the viscosity of the solution, involving problems in the upper limit varies depending upon the kind of the solvent Shaping operatiom of polyam1no acid solution, concentration of polyamino However, when the polyamino acid Solution in FA, acld or kmd of the Poor Solvent?- In case a DCP or 2,3-DCP according to the present invention is or solutlon of polyamino l used, the addition of the hydrophilic or hydrophobic solusually the upper 1s 20 to 30% based on the weig vents shown in Tables 3 through 6 does not result in an of the surpnsmgly It allowable to add especlal' increase in the viscosity of the solution and, on the con- Y ammatlc Solvent Such as benzene toluene Xylene trary, rather shows a decrease in viscosity. Further, the 111 an amount of 11P to 20,000% (200 fold); increase in the viscosity of the solution caused by the ad- Taifles 5 and Show the results when vanous hydro dition of a pigment paste is slight and does not involve phobfc Solvents are added to 15% and FA any problem in the shaping operation. This is also one of Solutlons and 20% d 1311301), Solutlons of the characteristics of the polyamino acid solution of the poly-ymethylglutamate (intrinsic viscosity: 1.5 and Present invention molecular Welght of m- Usually the above-mentioned poor solvents for polyamino acids are added after the preparation of the poly- TABLE 5 amino acid solution in FA, 1,3-DCP or 2,3-DCP. How- Concentration ofpoly. so ever, in case the polymerization reaction to prepare vv gi C polyamino acids 1s carried out 111 FA, 1,3-DCP or 2,3-

ma 6 n giififil DCP, it is possible to add such poor solvents before the Solvent 10% 1 0% (seconds) polymerization reaction. Ethyl acetate O A X 20.30 From the above description, it is understood that the iu y eg 33:23 5 polyamino acid solution according to the present invention niiliiif iiih'onas I 20.30 is very advantageous for the shaping of polyamino acids. g e v 8 8 O -28 The invention will be further understood from the zTc illi r l 111% g -53 ffillowing exaniiples aind are to lie Icionsiderecl as merely :1 one i ustrative an not imitative o t e presen invcn 10 giifii riigifii iiiifiifi: 2 as Obviously, various modifications are possible for those Ethylene y l monoethyl ether skilled in the art within the spirit of the present invention. E ii i '1' i "if; '1' 'th'" x X 30 yene 0O 11101101116 y 8 er rligetatefi g g? gt: EXAMPLE 1 I1- exan ae 7 Three kinds of poly-'y-methyl-L-glutamate polymers fTab1e6- having respective intrinsic viscosities of 1.0, 1.8 and 2.5

and containing almost no fl-configurations are obtained by adding methanol separately to three kinds of ethylene dichloride solutions of the polymers having different degrees of polymerization and precipitating the polymers with minimum mechanical stress. (In each case, the intrinsic viscosity and reduced viscosity are measured at 20 C. by dissolving the polymers in dichloroacetic acid. This same measurement procedure is applicable to each of the following examples and to the preceding experiments.) Also, polymers of almost 100% fi-configurations are obtained by preparing films from the three kinds of polayamino acid solutions by a dry process and stretching the films two fold. Further, polymers of about 50% fi-configurations are obtained by pulverizing the three kinds of polymers containing almost no B-configurations to less than 40 meshes with a hammer mill-type grinder.

Each of these polymers is dissolved in FA at room temperature so that the polymer solutions respectively have concentrations shown in Table 7. The resultant solutions are coated on polished glass plates with a doctor blade having a thickness of 3 mils inches) to form polymer solution layers. Coagulation time is measured in water at 20 C. The results are shown in Table 7. Thus, from any of 9 kinds of polymer solutions in Table 7, a film of poly-y-methyl-L-glutamate is obtained.

'8 Example 6 A poly-y-methyl-D-glutamate solution containing an excess FA in the solvent system is prepared by adding FA dropwise to a poly-v-methyl-D-glutamate solution in ethylene dichloride while distilling off the solvent therefrom under reduced pressure.

The thus-prepared solution is coated on a glass plate with a doctor blade of 3 mils to form a polymer layer. The coated layer is coagulated in water at 20 C. and dried to obtain a film.

Example 7 10% FA solution of poly-y-methyl-L-glutamate having an intrinsic viscosity of 1.8 is prepared. This solution is coated on polished glass plates with a doctor blade of 3 mils to form polymer layers and the coated layers are coagulated in coagulating baths respectively consisting of water and methanol (volume ratio 1:1), and water and acetone (volume ratio 1:1) at 25 C. After drying, transparent films are obtained.

Example 8 50 g., 100 g. and 2,000 g. each of benzene, toluene and xylene are added to each of 10 g. of 10% FA solu- TABLE 7 intrinsic viscosity fl-configurations, percent 0 ca. 50 ca- 1 0 c 50 ca. 100 0 ca. 50 ca. 100

' 25 20 15 12 10 10 8 Concentration of the solution, percent 20 20 20 0 2o 20 20 20 Coagulation time (seconds) Example 2 9 g. of FA is added at room temperature to each of 1 g. of poly-y-benzyl-tD-glu tamate having an intrinsic viscosity of 1:5, p0ly-y-ethyl-L-glutamate having a reduced viscosity of 2.0 and poly-'y-butyl-L-glutamate having a reduced viscosity of 1.0 separately to dissolve the polymers. Films are obtained from the resultant solutions according to the procedure described in Example 1.

Example 3 9 g. of FA is added separately to each of 1 g. of polye-carbobenzoxy-L-lysine (reduced viscosity: 2.0), polyfi-methyl-L-aspartate (reduced viscosity: 1.5), poly-L- leucine (reduced viscosity 2.4) and poly-L-alanine (reduced viscosity: 2.3), and the resultant mixtures are subjected to shaking and stirring at room temperature for about 8 hours. All of these polymers are completely dissolved. Films are obtained from these polymer solutions by coating the polymer solutions on glass plates with a doctor blade (thickness 3 mils) to form coated layers, coagulating in water at 20 C. and drying.

[Example 4 9.5 g. of FA is added to each of 0.5 g. of copolymers, [(y-methfl-L-glutamate and e-carbobenzoxy-L-lysine 1:1), ('y-methyl-L-glutamate and L-leucine 1:1) and (B- methyl-L-aspartate and e-carbobenzoxy-L-lysine 1:1)], and the resultant mixtures are subjected to stirring at room temperature for 8 to 24 hours. The respective copolymers are dissolved. Films are obtained according to the procedure described in Example 3.

Example 5 'y-methyl-D-glutamate-N-carboxy anhydride is charged into FA so as to make the polymer concentration after polymerization of 10%. Polymerization is carried out at a temperature of 20 C. using triethylamine as an initiator (the ratio of the monomer to the initiator=l00 by mole). A poly-'y-methyl-Dglutamate solution having a reduced viscosity of 0.5 is obtained.

tions of poly-y-methyl-L-glutamate having an intrinsic viscosity of 1.8, whereby uniform, transparent solutions are obtained. The polymer is insoluble in benzene, toluene or xylene, singly, in the absence of FA. The solutions are subjected to coagulation in a coagulating bath of acetone-water system (volume ratio 1:1). After drying, films are obtained.

Example 9 'y-methyl-L-glutamate-N-carboxy anhydride is charged into solvent systems of FA-ethylene dichloride [(5:5) and (7.5 :2.5), each ratio by weight] to make the respective polymer concentrations after polymerization of 10% Polymerizations are carried out at a temperature of 20 C. using triethylamine as an initiator (the ratio of the monomer to the initiator=l00 by mole). FA-ethylene dichloride solution of poly-'y-methyl-L-glutamate, each having a reduced viscosity of 0.8 and 0.6 are obtained.

Example 10 To 15% ethylene dichloride solution of poly-'y-methyl- L-glutamate having an intrinsic viscosity of 1.8 is added an equal amount of FA to obtain a homogeneous polyamino acid solution. The solution is coated on a glass plate with a doctor blade having a thickness of 3 mils and the coated layer is coagulated in water at 20 C. After drying, a film is obtained.

Example 11 no fi-configurations to less than 40 meshes with a hammer tion is coated on polished glass plates with a doctor blade mill-type grinder. of 3 mils to form polymer layers and the coated layers Each of these polymers is dissolved in 1,3-DCP at are coagulated in coagulating baths respectively consistroom temperature so that the polymer solutions have coning of methanol and water (volume ratio 1:1), water and centrations shown in Table 8. The resultant solutions are acetone (volume ratio 1:1) and methanol and water coated on polished glass plates with a doctor blade hav- 5 (volume ratio 2:8) at 25 C. After drying, transparent ing a thickness of 3 mils (V inches) to form polymer films are obtained. solution layers. Coagulation time is measured in water at Example 18 C. The results are shown in Table 8. From any of 9 kinds of polymer solutions in Table 8, a film of poly- 50 g., 100 g. and 2,000 g. each of benzene, toluene and 'y-methyl-L-glutamate is obtained by a wet process. 10 xylene are added to each of 10 g. of 10% 1,3-DCP solu- TABLE 3 Intrinsic viscosity B-eonfigurations, percent 0 ca. 50 05.100 0 ca. 60 ca. 100 0 ca. 50 ca. 100 8 g i tii ii iii ii s ii tig i ili f fii ffliiIIIIIIIIIIIIIIIII so-iiii 120-128 14o-1 8 100- iii 125-123 iso-liiii 110-138 130-138 120-138 Example 12 tions of poly-'y-methyl-L-glutamate having an intrinsic 2O viscosity of 1.8, whereby uniform, transparent solutions are obtained. The polymer is insoluble in benzene, toluene or xylene singly in the absence of 1,3-DCP. These solutions are subjected to coagulation in a coagulating bath of acetone-water system (volume ratio 1:1). After drying, films are obtained.

9 g. of 1,3-DCP is added at room temperature to each of 1 g. of polyy-benzyl-D-glutamate having an intrinsic viscosity of 1.5, poly-'y-ethyl-L-glutamate having a reduced viscosity of 2.0 and poly-' -butyl-L-glutamate having a reduced viscosity of 1.0 separately to dissolve the polymers. Films are obtained from the resultant solutions according to the procedure described in Example Example 19 v-methyl-L-glutamate-N-carboxy anhydride is charged Example 13 into solvent systems of 1,3-DCP and ethylene dichloride 9 .g. of 1,3-DCP is added separately to each of 1 g. [(55), and (713)! each ratio'by weight] to k of poly e carbobenzoxy L lysine (reduced viscosity; Z0), respective polymer concentrations after polymerization Po1y p methy1 L aspartate (reduced viscosity; 1,5), Po1y of 10%. Polymerlzations are carrled out at a polymeriza- L-leucine (reduced viscosity: 2.4) and poly-L-alanine (re- P P P 6 0 25 C. using triethylamine as an duced viscosity: 2.3), and the resultant mixtures are sublmtlator (the Tatlo of the q f to an 1n1t1atr=80 jected to shaking and stirring at room temperature for by 13'DcP":thY1ene dlihlonde solutlon's of P 3" about 12 hours. All of these polymers are completely dis- 'Y'methYLL'glutamaFe each havmg a reduced Vlscoslty of solved. Films are obtained from these polymer solutions and are obtamei by coating the polymer solution on glass plates with a E l 20 doctor blade (thickness: 3 mils) to form coated layers,

coagulating in water at 00 C and drying To 15% ethylene dichloride solution of poly-y-methyl- L-glutalnate having an intrinsic viscosity of 1.8 is added Example 14 an equal amount of 1,3-DCP to obtain a homogeneous 95 of 13 DCP is added to each of 05 of polyamino acid solution. The solution is coated on a glass polymers glutamate and e carbobenzoxy plate with a doctor blade having a thickness of 3 mils IAYSine 1.1), (,y methyl L glutamate and Lleucine and the coated layer is coagulated 1n water at 20 C. 1:1) and (ti-methyl L aspartate and e-carbobenzoXy-L- After drymg a film 1S obtamed' lysine-1:1)], and the resultant mixtures are subjected to Examples 21 to 24 stirring at room temperature for 8 to 24 hours. The respective copolymers are dissolved. Films are obtained ac- The Procedures descrlbed EXamPleS 11 to 14 are peated except that 2,3-DCP is used in place of 1,3-DCP.

cording to the procedure described in Example 13.

The results are similar to those obtained in Examples 11 Example 15 to 'y-methyl D glutamate N carboxy anhydride is Example 25 charged into a mixture of 1,3-DCP and 2,3-DCP (1:1) so as to make the polymer concentration after polymeriza- 20 and 50 each of toluene and Xylene are added a 228223 233522 riser assertin E1: ure 0 using triet y amine as an initiator (the ratio of the monomer to the initiator=70 by mole). A gf gig 331gf i gggfg g gi i i accordpoly-y-methyl-D-glutamate solution having a reduced visg p m amp 6 COSIlZY of 0.7 is obtained. Example 26 Example 16 To each of 1 g. of poly-' -benzyl-D-glutamate (intrinsic A poly-'y-methyl D glutamate solution containing ylsfosltyz poly'v'ethyl'L'glutamate (reduced an excess 1,3-DCP in the solvent system is prepared by cosity: poly'v'blityl'L'glutamate (reduced adding 13 DCP dropwise to a polywmgthyLuglutamate cosity: 1.0) is added a mixed solvent of 4.5 g. of FA solution in ethylene dichloride while distilling air the and Each the Pdymers 1S solvent th fr under reduced pressure solved. Films are obtained frorn these solutions according The thus-prepared solution is coated on a glass plate to the procedure descnbdm m i with a doctor blade of 3 mils to form a polymer layer. The From the abovefdetalled desFnptloPt 1t be coated layer is coagulated in Water at 200 C. and dried stood that the unique polyamino acid solutions of this to obtain a film invention are suitable for a wide variety of applications. Example 17 Also, the suitable polyamino acids which have a degree of polymerization of about 50 to 5,000 may be further 10% 2,3 -D CP solution of poly-y-methfl-L-glutamate I characterized as having molecular weight ranging from having an intrinsic viscosity of 1.8 is prepared. This soluabout 3,000 to about 1,000,000.

Furthermore, the polymer concentration of the polyamino acid solution may be up to about 70% by weight, based on the total weight of the solution.

What is claimed is:

1. A polyamino acid solution in a solvent system containing at least one solvent selected from the group consisting of furfuryl alcohol, 1,3-dichloro-2-propanol and 2,3-dichloro-1-propanol.

2. The polyamino acid solution of claim 1, wherein said solution contains 0.5 weight percent or more of said one solvent.

3. The polyamino acid solution of claim 1, wherein the concentration of said solution is up to about 70% by weight of polymer.

4. The polyamino acid solution of claim 2, wherein the polyamino acid is selected from the group consisting of homopolymers and copolymers of amino acids and derivatives of said amino acids having a degree of polymerization of 50 to 5,000, said amino acids or derivatives thereof being selected from the group consisting of w-alkyl and w-benzyl esters of acidic amino acids, the alkyl group having 1 to 8 carbon atoms, N-substituted basic amino acids, the substituent being selected from aromatic acyl groups having 7 to 8 carbon atoms, alicyclic acyl groups having 4 to 8 carbon atoms, aliphatic acyl groups having 2 to 8 carbon atoms, aromatic oxycarbonyl groups having 7 to 8 carbon atoms, alicyclic oxycarbonyl groups having 4 to 8 carbon atoms and aliphatic oxycarbonyl groups having 2 to 8 carbon atoms, neutral amino acids free of hydroxyl groups containing from 2 to 9 carbon atoms, D-alanine and L-alanine.

5. The polyamino acid solution of claim 1, wherein the solvent system also contains a poor solvent for said polyamino acid.

6. The polyamino acid solution of claim 5, wherein said poor solvent is a hydrophilic solvent.

7. The polyamino acid solution of claim 5, wherein the poor solvent is a hydrophobic solvent.

8. A process for providing a new polyamino acid solution which comprises forming a polyamino acid solution in a solvent system containing at least one solvent selected from the group consisting of furfuryl alcohol, 1,3- dichloro-Z-propanol and 2,3-dichloro-1-propanol.

9. The process of claim 8, wherein said solution contains 0.5 weight percent or more of said one solvent.

10. The process of claim 8, wherein the concentration of said solution is up to about 70% by weight of polymer.

11. The process of claim 9, wherein the polyamino acid is selected from the group consisting of homopolymers and copolymers of amino acids and derivatives of said amino acids having a degree of polymerization of 50 to 5,000, said amino acids or derivatives thereof being selected from the group consisting of w-alkyl and w-benzyl esters of acidic amino acids, the alkyl group having 1 to 8 carbon atoms, N-substituted basic amino acids, the substituent being selected from aromatic acyl groups having 7 to 8 carbon atoms, alicyclic acyl groups having 4 to 8 carbon atoms, aliphatic acyl groups having 2 to 8 carbon atoms, aromatic oxycarbonyl groups having 7 to 8 carbon atoms, alicyclic oxycarbonyl groups having 4 to 8 carbon atoms and aliphatic oxycarbonyl groups having 2 to 8 carbon atoms, neutral amino acids free of hydroxyl groups containing from 2 to 9 carbon atoms, D-alanine and L- alanine.

12. The process of claim 8, wherein the solvent system also contains a poor solvent for said polyamino acid.

13. The process of claim 12, wherein said poor solvent is a hydrophilic solvent.

14. The process of claim 12, wherein the poor solvent is a hydrophobic solvent.

15. The process of claim 11, wherein said solution is prepared by adding said at least one solvent to a solid polyamino acid and stirring at room temperature.

16. The process of claim 11, wherein the polyamino acid solution is prepared by adding said at least one sol- 12 vent to a solid polyamino acid and stirring with heating.

17. A process for forming a layer of a polyamino acid on a substrate which comprises forming a polyamino acid solution in a solvent system containing 0.5 wt. percent or more of at least one solvent selected from the group consisting of furfuryl alcohol, 1,3-dichloro-2-propanol and 2,3-dichloro-1-propanol, applying said solution to the substrate and thereafter removing the solvent system from said solution, said polyamino acid being selected from the group consisting of homopolymers and copolymers of amino acids and derivatives of said amino acids having a degree of polymerization of 50 to 5,000 and said amino acids or derivatives thereof being selected from the group consisting of w-alkyl and w-benzyl esters of acidic amino acids, the alkyl group having 1 to 8 carbon atoms, N"- substituted basic amino acids, the substituent being selected from aromatic acyl groups having 7 to 8 carbon atoms, alicyclic acyl groups having 4 to 8 carbon atoms, aliphatic acyl groups having 2 to 8 carbon atoms, aromatic oxycarbonyl groups having 7 to 8 carbon atoms, alicyclic oxycarbonyl groups having 4 to 8 carbon atoms and aliphatic oxycarbonyl groups having 2 to 8 carbon atoms, neutral amino acids free of hydroxyl groups containing from 2 to 9 carbon atoms, D-alanine and L- alanine.

18. The polyamino acid solution of claim 4, wherein said one solvent is 1,3-dichloro-2-propanol.

19. The polyamino acid solution of claim 4, wherein said one solvent is 2,3-dichloro-1-propanol.

20. The polyamino acid solution of claim 4, wherein said solvent system consists essentially of at least one solvent selected from the group consisting of furfuryl alcohol, 1,3-dichloro-2-propanal and 2,3-dichloro-1-propanol.

21. The polyamino acid solution of claim 20, wherein said solution has a concentration up to about 70% by weight of said polyamino acid.

22. The process of claim 11, wherein said one solvent is 1,3-dichloro-2-propanol.

23. The process of claim 11, wherein said one solvent is 2,3-dichloro-1-propanol.

24. The process of claim 11, wherein said solvent systern consists essentially of at least one solvent selected from the group consisting of furfuryl alcohol, 1,3-dichloro-2-propanol and 2,3-dichloro-1-propanol.

25. The process of claim 11, wherein said solution has a concentration up to about 70% by weight of said polyamino acid.

26. The process of claim 17, wherein said one solvent is 1,3-dichloro-2-propanol.

27. The process of claim 17, wherein the one solvent is 2,3-dichloro-l-propanol.

28. The process of claim 17, wherein said polyamino acid solution has a concentration up to about 70% by weight of said polyamino acid.

References Cited UNITED STATES PATENTS 3,369,026 2/1968 *Iwatsuki 260307 3,554,944 1/1971 Helm 26018 3,679,638 7/ 1972 Helmuth 2607 8 S 3,089,749 4/ 1963 Ballard 18--54 3,006,899 10/ 1961 Hill 26078 2,882,186 4/1959 Schoenberg 117-161 OTHER REFERENCES Solubility Parameters for Film Formers, Burrell, pp. 726-727 and pp. 740-751, 1955. 4

Technology of Paints, Reinhold, New York, 1968, pp. 286-291.

ALLAN LIEBERMAN, Primary Examiner R. ZAITLEN, Assistant Examiner US. Cl. X.R. 26033.4 R 

